Coffee Husk Biochar: A Sustainable Amendment for Soil Acidity Mitigation and Carbon Sequestration
Haile Hasana
*
Department of Natural Resource Management, Sidama Agricultural Research Institute, Hawassa, Ethiopia.
*Author to whom correspondence should be addressed.
Abstract
Coffee husks are the most abundant biomass waste generated by coffee processing plants. Converting this waste into biochar is an emerging and promising approach for reclaiming acidic soils and enhancing carbon sequestration. This paper provides an overview of the characteristics of coffee husk biochar (CHB) and its effects on soil properties, liming and agronomic potential, and environmental impacts. Application of CHB produced at different pyrolysis temperatures and application rates increased soil pH, organic carbon, and the availability of P, K⁺, and Ca²⁺ in acidic soils, while significantly reducing exchangeable acidity and the concentrations of Al³⁺ and H⁺. The high ash content of CHB, together with the presence of KHCO₃ and CaCO₃, contributes to its strong liming potential in acidic soils. Furthermore, CHB produced at moderate pyrolysis temperatures (350–550 °C) exhibited high cation exchange capacity (CEC), indicating its potential to improve soil nutrient retention, reduce greenhouse gas emissions, and enhance carbon sequestration, thereby reducing dependence on agricultural lime. Overall, this review synthesises current knowledge on the effects of CHB on soil properties and highlights its potential role in mitigating soil acidity and climate change. The findings provide valuable insights for researchers, practitioners, and farmers seeking sustainable strategies to improve acidic soils using CHB. However, as most existing studies have been conducted under controlled conditions, further research across diverse soil types and agroecological zones is required to fully understand the long-term impacts and practical applicability of CHB.
Keywords: C sequestration, soil acidity, biomass, pyrolysis, biochar